Electrically conductive proppant coating and related methods

Abstract

An electrically conductive proppant coating and a method for applying the coating to the proppant, whereby the coated electrically conductive proppant can determine formation characteristics, such as dimensions, orientation, and conductivity.

The invention claimed is: 
     
       1. A method for determining geometry of a fracture in a subterranean formation, the method comprising:
 a. injecting a coated proppant into the fracture to cause the fracture to function as an emitting antenna while opening the fracture or holding the fracture open, the coated proppant including a proppant suspended in an electrically-conductive coating, the electrically-conductive coating (i) deposited on a proppant surface of the proppant, (ii) stabilized with an oxidizing agent, and (iii) including a mixture of carbon residue forming material and a solvent, the coated proppant carbonized and graphitized, the carbon residue forming material being petroleum pitch, the solvent being toluene, xylene, quinoline, tetrahydrofuran, tetralin, or naphthalene; 
 b. sending, via electrical connections, a time-varying electrical signal into the fracture to charge the coated proppant, the time-varying electrical signal generated at a top surface above the fracture; 
 c. detecting, via a plurality of surface antennas at the top surface, the time-varying electrical signal, the plurality of surface antennas spaced from each other over an area above the fracture; and 
 d. determining the geometry of the fracture based on the time-varying electrical signal detected by the plurality of surface antennas. 
 
     
     
       2. The method according to  claim 1 , wherein the solvent is toluene. 
     
     
       3. The method according to  claim 1 , wherein the solvent is xylene. 
     
     
       4. The method according to  claim 1 , wherein the electrically-conductive coating is graphitized immediately after being carbonized. 
     
     
       5. The method according to  claim 1 , wherein the electrical connections extend from the surface of the fracture to a well casing. 
     
     
       6. The method according to  claim 1 , wherein the electrical connections extend to a mud pit. 
     
     
       7. The method according to  claim 1 , wherein the time-varying electrical signal is generated via a reversing DC current. 
     
     
       8. The method according to  claim 1 , wherein the time-varying electrical signal is generated via an AC current. 
     
     
       9. The method according to  claim 1 , wherein the detecting the time-varying electrical signal includes recording the time-varying electrical signal. 
     
     
       10. The method according to  claim 1 , wherein the plurality of surface antennas are spaced from each other over different parts of the fracture. 
     
     
       11. The method according to  claim 1 , wherein the oxidizing agent is a gaseous oxidizing agent. 
     
     
       12. The method according to  claim 11 , wherein the gaseous oxidizing agent is selected from a group consisting of oxygen, sulfur fumes, gaseous oxides, nitrogen oxide gas, ambient air, halogens or combinations thereof. 
     
     
       13. A method for determining geometry of a fracture in a subterranean formation, the method comprising:
 a. injecting a coated proppant into the fracture, the coated proppant including a proppant suspended in an electrically-conductive coating material deposited on a surface of the proppant and stabilized with an oxidizing agent, the coated proppant carbonized and graphitized; 
 b. sending a time-varying electrical signal into the fracture to charge the coated proppant; 
 c. detecting, via a plurality of surface antennas, the time-varying electrical signal, the plurality of surface antennas spaced from each other over an area above the fracture; and 
 d. determining the geometry of the fracture based on the time-varying electrical signal detected by the plurality of surface antennas. 
 
     
     
       14. The method according to  claim 13 , wherein the coating material includes a mixture of carbon residue forming material and a solvent or combination of solvents. 
     
     
       15. The method according to  claim 14 , wherein the carbon residue forming material is petroleum pitch. 
     
     
       16. The method according to  claim 14 , wherein the solvent or combination of solvents is selected from a group consisting of toluene, xylene, quinoline, tetrahydrofuran, tetralin, naphthalene or combinations thereof. 
     
     
       17. The method according to  claim 13 , wherein the coated proppant is injected into the fracture during creation of the fracture. 
     
     
       18. The method according to  claim 13 , wherein the plurality of surface antennas are spaced from each other over different parts of the fracture.